(1) Field of the Invention
The present invention relates generally to omnidirectional vehicles and more particularly relates to a drive mechanism for an omnidirectional vehicle.
(2) Background Information
Omnidirectional vehicles capable of controlled motion in any planar direction have long been recognized as advantageous for many potential applications, such as those in commercial, medical, industrial, and recreational settings. Many, if not most, omnidirectional vehicles are similar in that they utilize wheels featuring rollers positioned about the periphery thereof. The rollers permit the wheels to support motion in directions at a nonzero angle to the wheel""s plane of rotation (e.g., orthogonal thereto). Omnidirectional vehicles using the above-described wheels may typically move in any direction by rotating the wheels and rollers in combination. For example, as described by Ilon (in U.S. Pat. Nos. 4,598,782 and 3,876,255) each wheel""s rotation is mechanically driven and servo controlled in a coordinated fashion to cause the vehicle to follow a desired path. Over the years numerous improvements to Ilon""s wheel have been disclosed. For example, Harris (in U.S. Pat. No. 6,340,065) recently disclosed a potentially improved wheel assembly including a hub on which free spinning rollers are rotatably mounted at an angle to the wheel axis. The Harris wheel assembly is purported to provide for a relatively constant ride height and low vibration operation by configuring the rollers with an exterior profile, thickness, material properties and surface grooving to achieve constant deflection of the roller contact surface at all wheel rotation angles. Nevertheless, despite the improvements thereto, the above approaches tend to be disadvantageous in that they require relatively complex wheels.
One approach to constructing a highly maneuverable vehicle is to provide the vehicle with two independent conventional drive wheels and one or more casters. While this approach may allow for a zero turning radius, it does not provide for truly omnidirectional motion. An alternate approach to an omnidirectional vehicle is to couple conventional wheels to a steering link, which is coupled to the vehicle chassis and rotatable about a vertical axis. While this approach tends to allow for omnidirectional motion, it tends not to be holonomic in that it may not always be possible to change direction in a continuous manner, e.g., a discontinuous change in translational direction may require the vehicle to stop while the wheels are steered.
Therefore, there exists a need for an improved vehicle and/or drive mechanism that typically utilizes conventional wheels and that provides for omnidirectional, holonomic motion.
One aspect of the present invention includes a drive mechanism. The drive mechanism includes at least one tracking device assembly rotatably coupled about a tracking device assembly axis to a chassis, the tracking device assembly including a plurality of tracking devices coupled to a tracking device assembly chassis. The drive mechanism further includes a tracking device constraint module coupled to the tracking devices, the tracking device constraint module being configured to control orientation of the tracking devices, and the tracking device assembly configured for being rotatably driven about the tracking device assembly axis.
Another aspect of the present invention includes a drive mechanism. The drive mechanism includes at least one wheel assembly rotatably coupled about a wheel assembly axis to a vehicle chassis, the wheel assembly including a plurality of wheels coupled to a wheel assembly chassis. The drive mechanism further includes a wheel constraint module coupled to the wheels, the wheel constraint module being configured to control orientation of the wheels, and the wheel assembly configured for being rotatably driven about the wheel assembly axis.
In still another aspect, this invention includes a vehicle. The vehicle includes at least one wheel assembly rotatably coupled about a wheel assembly axis to a vehicle chassis, the wheel assembly including at least two wheels coupled to a wheel assembly chassis. The vehicle further includes a wheel constraint module coupled to the wheels, the wheel constraint module being configured to control orientation of the wheels and a power module coupled to the wheel assembly, the power module configured to rotate the wheel assembly about the wheel assembly axis.
In yet another aspect, this invention includes a method of propelling a vehicle. The method includes using a vehicle including at least one wheel assembly rotatably coupled about a wheel assembly axis to a vehicle chassis, the wheel assembly including at least two wheels coupled to a wheel assembly chassis, a wheel constraint module coupled to the wheels, the wheel constraint module being configured to control orientation of the wheels. The method further includes rotating the wheel assembly about the wheel assembly axis, and actuating the constraint module to effect a change in orientation of at least one of the wheels.
In a further aspect, this invention includes a method of fabricating a vehicle. The method includes forming at least one wheel assembly including at least two wheels coupled to a wheel assembly chassis and rotatably coupling the wheel assembly to a vehicle chassis. The method further includes coupling a power module to the wheel assembly, the power module configured to rotate the wheel assembly about the wheel assembly axis, and coupling a wheel constraint module to the wheels, the wheel constraint module being configured to control orientation of the wheels.